The name was a joke.
In 1874 a practical joke started in New York when someone said to an other: “Tom Collins says that you are an idiot” and the victim asked “where is this Tom?” and the author directed him to the nearest bar, where the fictive “Tom Collins” where suposed to be. And when the poor victim entered the location asking furously after “Tom Collins” people would laugh since there where no person with this name.
The hoax became so common that Jerry Thomas named a drink after this, which he describes in 1876 in his “The Bartender’s Guide” as a “Tom Collins” made with either Whisky, Brandy or Gin.
The Jerry Thomas “Tom Collins Gin” recipe from 1876:
Use large bar-glass
Take 5 or 6 dashes of gum syrup
Juice of a small lemon
1 large wine-glass of gin.
2 or 3 lumps of ice
Shake well and strain into a large barglass. Fill up the glass with soda water and imbibe while it is lively.
In 1880 at the Limmers Hotel in London the bartender John Collins makes a similar drink with Old Tom Gin where as some people think that this was the burth af the Tom Collins (Old Tom/John Collins = Tom Collins), but since this goes on 4 years later than the story above, there can be no doubt about the origin of the name and the recipe.
In 1891 the book “The Flowing Bowl: When and what to Drink” by William Schmidt describes this version of a “Tom Collins Gin” as follows:
The juice of half a lemon in a large glass,
a bar-spoonful of sugar,
a drink of Tom gin; mix this well;
2 lumps of ice
a bottle of plain soda
Mix well and serve.
Today the most common interpretation of the Tom Collins is very close to the original by Jerry Thomas – which translated into the terms of this century goes like this:
3 Gin
2 Lemon juice
1 Sugar syrup
Soda water
Lemon slice for garnish
Pick a good dry gin without to much juniper to match the sweet and the sour ingredients.
Pour the gin, lemon juice and sugar syrup into a highballer with ice cubes and stir. Top with soda water and make sure that theres a nice layer of foam. Garnish with the lemon slice.